Process for roasting ores.



UNITED STATES PATEN OFFICE.

CHARLES GABRIELLI, OF PARIS, FRANCE.

YROCESS FOR BOAS'IING OBES.

1,018,609. No Drawing.

is a sulfid, it is generally necessary to first roast the ore so that acompound of the metal will be formed which is soluble in water or in asolution of an acid. In other cases, the ore is first roasted to obtainthe metalloid combined with the metal and the residue is then treated torecover the metal contained therein. Let us take for examplethe morecomplex case of copper pyrites, which is roasted with a View to theproduction of sulfuric acid and consider the general operations:employed for the recovery of the copper. As is known in the manufactureof sulfuric acid either by the lead chamber process or by the contactprocess, the copper pyrites is usually roasted in Maletra or mechanicalfurnaces, the Maletra-furnaces -being used for ores which are poor insulfur. To obtain a good yield of acid, it is necessary to carry on theroasting in a manner which will give a fixed composition of gas, but inthis case the residue is not in a good condition for the recovery of thecopper. Thus when the residue of the copper pyrites from the furnace istreated by the wet-' process, after being roasted in any usual manner itstill contains some quantity of copper in an insoluble state and also aquan tityof iron passes into the liquor and adds to the amount of ironwhich is precipitated so that a very impure precipitate is obtained. Toavoid these inconveniences many processes are employed in practice suchas treatment with a chlorid or with a sulfate such as ferric sulfate orferrous sulfate, or with sulfuric acid and the like. These treatmentsconsist in grinding the residue of Specification of Letters Patent.Application filed. November 15, 1910. Serial No. 592,587.

Patented Feb. 27, 1912.

the roasted pyrites to either mix it with a chlorid having a lowertemperature of dissociation than the temperature of the formation ofcupric chlorid CuCl or to mix it with ferric or ferrous sulfate or withsulfuric acid or the like. The mixture is then placed in a specialfurnace where the reaction takes place at a temperature between 400 and500 C. These known methods assist in giving a better yield of metal, butthey leave nevertheless a considerable quantity of the metal in theresidues; besides the carrying out of.the difl'erent operations is veryexpensive.

The object of the present invention is a process of roasting the pyritesor sulfid ores, matte, or the like which will give, at the sameoperation and direct from the pyrites residue, a compound of the metalwhich is soluble in water or acid solution and thus nearly all the metalcan be extracted by the wet process without submitting the pyritesresidue to any further reactions, treatment or roasting.

This process consists in adding a certain quantity of green pyrites tothe dead roasted pyrites on a hearth or at a part of the roastingfurnace where thetemperature is between that which is necessary for theformation of the sulfates of the metal to be sepa rated and that atwhich the said sulfates decompose. Thus in the case where greater heatis required for the formation of the sulfate which it is desired todissolve than is necessary for the formation of the sulfate to be keptinsoluble, the hearth or that part of the furnace where the greenpyrites is added to bring about the production of the sulfate, must beat a lower temperature than that which would decompose the sulfate ofthe metal which it is desired to dissolve in water or in an acidsolution but it must have a higher temperature than that at which thesulfate of the metal which it is desired to keep insoluble willdecompose. In the opposite case that is to say, when less heat isrequired for the formation of the sulfate of the metal to be dissolvedthan is necessary for the formation of the sulfate ofthe metal desiredto remain insoluble, the

temperature of the hearth or of thepart of the furnace at which theformation\of the sulfates takes place, should be higher than thetemperature required for the formatlon of the sulfate of the metal to bedissolved but lower than the temperature required for recovering from itthe metals contained in the residue.

The process described produces a particular chemical action by the,introduction and bringing about of a new reaction during the roasting ofthe .pyrites, z. e., the production of a sulfate at a particular pointof the furnace and at a temperature which is determined bythetemperatures at which the sulfates of the metal to be separated areformed or decomposed. Moreover this rocess produces new technicalresults an has the following practical and industrial advantages. Theyield from the pyrites thus roasted is higher than at present aspractically the whole is converted into sulfate and almost all the metalcontained therein is extracted and recovered by the wet process, theyield varying from 90% to 100% according to the nature of the ore. Thereis no need of any further treatment of the residue as is the case withthe other processes but the sulfate is separated by the wet process-directly from the residue obtained by asingle roasting. It does notdisturb the arrangement of the chambers when it is desired to obtain themetalloid. Moreover in consequence of the elimination of the costlyprocesses and the increased yield this process is very economical andadvantageous.

To better explain the idea of the invention I will hereinafter describeby way of example the application of the process, to the complex case ofthe roasting of copper pyrites in a Maletra-furnace with the ob ect ofobtaining sulfuric acid or recovering the copper.

Practlcally all the metals can be turned directly into sulfates in thefurnace if the reaction obtained by the addition of green pyrites iscarried out at the right temperature.

In order to obtain the copper as a sulfate the residue of the pyritesmust not be heated to the decomposing point but the temperature has tobe kept at the degree at which the sulfate of iron will decompose whilethe sulfate of the copper will not be influenced. Thus practically allthe copper can be changed into sulfate by adding green pyrites to thedead roasted pyrites at a determined the sul ur is practically completeand where the pyrites 1s heated to the temperature which is necessaryfor the artial change into sulfate, 2'. e., into the su fate of one ofthe two metals to be separated, it is possible to carry out this rocessin any ordinary roasting furnace. suppose that in a furnace of theMaletratype the favorable place for obtaining the sulfate ofsthe copperis the fifth hearth. This reaction can therefore take place at thisprecise part.

The roasting carried out according to this invention will result inobtaining nearly all the copper as a sulfate in water or in an acidsolution, nearly all the ironremaining insoluble. By this process theiron and copper in the pyrites are first changed into oxids and from theoxids the sulfates are produced by adding green pyrites on the hearth orthe part of the furnace where the temperature is higher than that atwhich the sulfate of iron will decompose but lower than that bus forexample let us treatment of the residue as the reaction takes place inthe furnace during roasting without interfering with the working of thechambers.

I claim 1. A process for roasting pyrites, ores, matte, residues and thelike containing sulfur in order to separate one or more of the metalscontained therein, consisting in adding green pyrites to the deadroasted pyrites at a part of the furnace where the temperature isbetween that required for the formation of the sulfates of the metals tobe separated, and the temperature at which said sulfates decompose,substantially as described and set forth.

2. Process for separating copper from perature at which the sulfate ofiron is pyrites, matteand the like, consisting in formed, substantiallyas described and set adding green pyrites during the roasting to forth.

the dead roasted'pyrites when the same is at CHARLES GABRIELLI. 5 a partof the furnace where the temperature In presence of is lower than thatat which the sulfate of the H. G. Coxn,

copper decomposes but higher than the tem- VICTOR MARENDOWSKI.

